Bidirectional selective remote control system



Sept. 14, 1948. KQGANE 2,449,391

BIDIRECTIONAL SELECTIVE REMOTE CONTROL SYSTEM Filed Jan. 21. 1948 10-51mm l0 7 mi] FILTERS f F' f F p F F A u A M STATION A MIXERS M, (M

OSCILLATORS F, O, 1 F 0 A F3 03 AL F4 04 n I l k- -l/a s 8 s l 3 5 v vS7 OSCILLATORS F5 05 06 F35 08 STATION 8. MIXERS -1 LMG M, L M

' Y W f FILTERS f F r F f F f F' Inventor":

.Lon Kogan e,

by MAM His Attorney.

Patented Sept; 14, 1948 BIDIRECTIONAL SELECTIVE itEMOTE CONTROL SYSTEMLeon Kogane, Paris, France, assignor to General Electric Company, acorporation of New York Application January 21, 1948, Serial No. 3,464In France June 22, 1945 Section 1, Public Law 690, August 8, 1946 Patentexpires June 22, 1965 1 2 Claims. 1

My invention relates to a frequency selective remote control systemwhich may utilize either wire lines or a space radio channel and whichpermits simultaneous transmission of one or more control signals ineither direction.

A system embodying the invention may comprise two spaced controlstations with generators,

at each station for generating a plurality of control frequency signals.These signals may be impressed in any combination on a commonbidirectional signal channel interconnecting the stations.

Apparatus is then provided so that for each signal supplied from onestation a selected control operation takes place at the other stationand without any interference with other control operations performedsimultaneously in the same or oppositedirection. An important feature ofthe invention resides in the fact'that a common beat frequency isutilized to efiect all the control operations and therefore thecontrolled apparatus at each station may include many identicalcomponents.

It is therefore a mainobject of my invention to provide an improvedbidirectional remote control system which permits a plurality ofselective control operations to be effected either sequentially orsimultaneously without any possibility of interference.

It is a further object of my invention to provide an improved frequencyselective remote control system which is simple and inexpensive andrequires a minimum of components.

For additional objects and advantages, and for a better understanding ofthe invention, attention is now directed to'the following descriptionand accompanying drawings, and also to the appended claims in which thefeatures of the invention believed to be novel are particularly pointedout.

The single figure of the drawing is a simplified schematic diagram of aremote control system embodying the invention.

Referring to the drawing, the system is illustrated as comprising twoseparate stations, station A and station E. The two stations are verysimilar and corresponding elements have been indicated by correspondingreference letters and numerals.

I Station A includes a plurality of oscillation generators. While anydesired number may be utilized, it is represented as comprising fouroscillators O1O4 whose output frequencies are l b-F4, respectively. Eachof the oscillator outputs is supplied to one input of a frequencyconverter or Mixer Ml-M, respectively Each of the mixer outputs issupplied through a filter F to any 2 suitable control device,represented conventionally as a relay Ill. All of the filter networksmay be identical and tuned to pass the same frequency f, and likewiseall of the control devices l0 may be identical if desired. The secondinput to each of the mixers is supplied from av common signaltransmission channel ll interconnecting the two stations. The dashedconnection Ila is used to indicate schematically that theinterconnection may be made either by means of wire lines or by atwo-way space radio channel. The output of each of the oscillators Oi-O4may also be selectively impressed upon the common transmission chan--gel bg closing a corresponding switch in the groups The elements ofstation B are practically identical in their arrangement to the elementsof station A. It includes the same number of oscillators 05*08, togetherwith corresponding mixers 1'VI]cMa and output filters F and controldevices quencies Ft-Fa, may likewise be selectively supplied to thecommon transmission channel ll through operation of switches -38.

It will be understood that each of the oscillators OlOB may be of anysuitable construction known to the art. The mixers Ml-Mii may likewisecomprise any suitable known forms of electron discharge device circuits,dry-rectifier bridges, or the like. For reasons that will shortlyappear, the filters F are preferably resonant networks each adapted topass frequency f and having a medium quality factor, or Q.

In the illustrated embodiment of the invention, the four oscillatorfrequencies at each station are different from each other and alsodifferent from the frequency f to which the filters are tuned.Therefore, these frequencies are not transmitted through the filters atthe same station and do not actuate the control devices ID at thatstation. Furthermore, the oscillator frequencies are so selected thatone beat frequency produced by combining F1 with F5, F2 with F6, F3 withP1, and F4 with Fe in each case is equal to I. For example, in onesuitable form, the relationships may be:

F1Fs:f FaF'1=f F2Fe=f F4-Fs:j

As a further condition, the beat frequencies resulting from combiningany one oscillator frequency at one station with any other oscillatorfrequency at either station must be such as to include only onecombination that results in the filter frequency f, and that must beproduced in The outputs of oscillators 05-08, at fre-' 3 combinationwith an oscillator frequency at the opposite station.

The application of these principles and the operation of the system willbe more easily understood by reference to a specific example. Forinstance, assume that the frequencies of the eight oscillators in thedrawing are as follows:

Cycles per second F1 800 F: 1200 F2=' 900 Fs=1300 F =1000 F1=1400F4=1100 Fa=1500 opposite station will be actuated. For example,

if Si is closed, an 800 C. P. S. signal is impressed upon all of themixers through the common transmission channel. However, only at themixer M5 will an output at the difference frequency of 400 cycles beproduced, actuating the.

associated control device 10. Inspection will show that a similar resultfollows when any one or more switches at either station are closed.

In the example selected for illustration it will be observed that thebeat frequencies produced at the outputs of the various mixers have afrequency separation in all cases of at least 100 C. P. S. If thefilters each comprise a simple resonant circuit tuned to 400 C. P. S.,the closest frequency to be rejected will have a divergence of at least100 C. P. S., corresponding to a detuning of 25%. If.the filter has amedium value of Q of at least 50, the attenuation of the closestundesired signal will then be of the order of 25. It is of coursedesirable not to use filters of too high a Q in order to permit the useof oscillators whose frequencies may vary slightly. For a gain variationof not more than 3 decibels, the effective pass band 2A is equal to f/Q.In the example arbitrarily selected for illustration, this is a passband of about 400/50, or approximately 8 C. P. S. For the highest localfrequency uti lized in the above example (i. e. 1500 C. P. 8.), thispermits a variation in oscillator frequency of about 0.5% which iseasily secured in ordinary oscillator design.

Inspection will show that it would be possible, if desired, to utilizesum frequencies rather than difference frequencies for control purposes,but in general the difference frequency is to be preferred since itreduces the range of frequencies which the transmission channel must bedesigned to convey.

The frequency relationships utilized in the practice of the presentinvention may again be summarized briefly as follows:

(1) All of the oscillator frequencies at any one station must bediflerent from each other and'from the filter pass frequency.

(2) The oscillator frequencies must also be so selected that the beatfrequencies produced by combining any selected oscillator frequencyatone station with any other oscillator frequency at either stationinclude only one combination at the selected beat frequency, and thatcombination must result with an oscillator frequency at the oppositestation.

(3) To utilize all the oscillators at each station, there must be asmany combinations pro- 4 duced at the desired beat frequency as thereare oscillators at each station.

While a specific embodiment has been shown and described, it will ofcourse be understood that various modifications may be made withoutdeparting from the invention. claims are therefore intended to cover anysuch modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A bi-directional selective remote control system comprising a pair ofseparated control stations, a plurality of oscillation generators at onestation, a corresponding number of oscillation generators at the otherstation, the frequencies of the generators at each station differingfrom each .other and from a selected beat frequency, said frequenciesbeing so selected that the beat frequencies produced by combining anyselected generator frequency at one station with any other generatorfrequency at either station include only one combination at saidselected beat frequency and that with a generator frequency at the otherstation, a corresponding number of frequency converters at, each stationeach having one input connected to a common signal transmission channelinterconnecting said stations and a second input energized from arespective generator, a frequencyselective control circuit connected tothe output of each of said converters, said circuit being adapted torespond to said selected beat frequency and substantially to attenuateother beat frequencies, and switching means for selectively impressingany one or more of said generator frequencies upon said common channel.

2. A bi-directional selective remote control system comprising .a pairof separated control stations, a plurality of oscillators at onestation, a corresponding number of oscillators at the other station, thefrequencies of the oscillators at each station differing from each otherand from a selected difference frequency, said frequencies being soselected that the difference frequencies produced by combining anyselected oscillator frequency at one station with any other oscillatorfrequency at either station include only one combination at saidselected difference frequency and that with an oscillator frequency atthe other station, there being as many pairs of such combinationsproducing said selected difierence frequency as the number ofoscillators at each station, a corresponding number of mixers at eachstation each having two inputs and an output, one input of each mixerbeing supplied from a common signal transmission channel interconnectingsaid stations, said channel being capable of transmitting all saidgenerator and difference frequencies in either direction,

the other input of each mixer being supplied from a respectiveoscillator, a control circuit connected to the output of each mixer,each control circuit including a filter tuned to pass only said selecteddifference frequency Without substantial attenuation, and switchingmeans for selectively impressing any one or more of said oscillatorfrequencies on said one input of all said mixers simultaneously throughsaid common channel.

LEON KOGANE.

The apppended

